Electronic circuit comprising PN junction and schottky barrier diodes

ABSTRACT

A semiconductor device includes a first chip including a PN junction diode, and a second chip including a Schottky barrier diode, connected in parallel to the first chip. A first inductive metal member has a first end connected to a cathode of the PN junction diode, and a second end connected to a cathode of the Schottky barrier diode. A second inductive metal member has a third end connected to the cathode of the Schottky barrier diode. An output line is connected to a fourth end of the second connection member, and electrically connected to the cathode of the PN junction diode via a first path formed by the first and second metal members, and to the cathode of the Schottky barrier diode via a second path formed by the second metal member and exclusive of the first metal member, so that the first path has greater inductance than the second.

CROSS-REFERENCE TO RELATED APPLICATIONS

This s application is a continuation of co-pending U.S. application Ser.No. 13/700,129, filed on Nov. 26, 2012, which is, in turn, a nationalstage of PCT application number PCT/JP2011/062233, filed May 27, 2011.Furthermore, this application claims the foreign priority benefit ofJapanese application number 2010-121375, filed on May 27, 2010. Thedisclosures of these prior applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to an electronic circuit such as aninverter circuit or a converter circuit.

BACKGROUND ART

A MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is used asa switching element of an electronic circuit, such as an invertercircuit or a converter circuit. A PN junction diode (body diode) that isa bipolar device parasitizes the MOSFET. In an electronic circuit inwhich the MOSFET is used, there is a fear that, if an electric currentflows through the PN junction diode (body diode) parasitizing theMOSFET, device properties will be deteriorated. In detail, if anelectric current flows through the PN junction diode, and if the MOSFEThas a crystal defect area, there is a fear that an electron and a holewill be recombined together in the crystal defect area, and the crystaldefect area will be enlarged.

Especially in an SiC MOSFET made or an SiC-based semiconductingmaterial, if an electric current flows through a PN junction diode, aforward direction deterioration (hereinafter, referred to simply as a“forward deterioration”) will be caused. In more detail, it is knownthat an SiC semiconductor crystal has a crystal defect that is called“BPD (Basal Plane Dislocation).” The crystal structure of a BPD part ischaracterized in that the band gap of its crystal is smaller than theoriginal band gap of an SiC semiconductor, unlike the crystal structureof the other parts. Therefore, the BPD part is liable to become arecombination center of an electron and a hole. Therefore, if a forwardcurrent flows through a PN junction part, BPD will be enlarged, and willcause a stacking fault. As a result, the on-resistance of the SiC MOSFETwill be increased.

Therefore, in order to prevent an electric current from flowing throughthe PN junction diode, a proposal has been made to provide a circuitstructure in which a Schottky barrier diode whose operating voltage islower than that of the PN junction diode is connected in parallel to thePN junction diode.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Published Unexamined Patent Application. No.2006-310790

BRIEF SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, even when such a circuit structure in which the Schottkybarrier diode is connected in parallel thereto is employed, a phenomenonin which an electric current flows through a PN junction diode hasoccurred. The inventor of the present application has discovered thatthis phenomenon is caused by a parasitic inductance of a current pathpassing through the Schottky barrier diode. In other words, when anelectric current starts flowing through the Schottky barrier diode, acounter electromotive force is generated by a parasitic inductance of acurrent path passing through the Schottky barrier diode. When thiscounter electromotive force reaches a forward voltage of the PN junctiondiode connected in parallel to the Schottky barrier diode, an electriccurrent flows through the PN junction diode.

It is an object of the present invention to provide an electroniccircuit capable of restraining an electric current from flowing througha bipolar device.

Means for Solving the Problems

The electronic circuit of the present invention includes a bipolardevice, a unipolar device connected in parallel to the bipolar device,and an output line connected to the bipolar device and to the unipolardevice. An inductance between the unipolar device and the output line issmaller than an inductance between the bipolar device and the outputline.

The aforementioned or other objects, features, and effects of thepresent invention will be clarified by the following description ofembodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electric circuit diagram showing an inverter circuitaccording to a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing an internal structure of amodule of FIG. 1.

FIG. 3 is a schematic side view showing an internal structure of apackage of FIG. 2.

FIG. 4 is an electric circuit diagram showing an inverter circuitaccording to a second embodiment of the present invention.

FIG. 5 is an electric circuit diagram showing an inverter circuitaccording to a third embodiment of the present invention.

FIG. 6 is an electric circuit diagram showing an inverter circuitaccording to a fourth embodiment of the present invention.

FIG. 7 is an electric circuit diagram showing a converter circuitaccording to a fifth embodiment of the present invention.

FIG. 8 is an electric circuit diagram showing a converter circuitaccording to a sixth embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

An embodiment of the present invention provides an electronic circuitthat includes a bipolar device, a unipolar device connected in parallelto the bipolar device, and an output line connected to the bipolardevice and to the unipolar device. An inductance between the unipolardevice and the output line is smaller than an inductance between thebipolar device and the output line. The bipolar device may be a PNjunction diode. The unipolar device may be a Schottky barrier diode.

A connection mode in which the bipolar device and the output line areconnected together may be either a first connection mode or a secondconnection mode as follows. In the first connection mode, the bipolardevice is connected to the unipolar device by means of a connectionline, and the unipolar device is connected to the output line by meansof another connection line. In the second connection mode, the bipolardevice is connected to the output line without being connected to theunipolar device. In other words, the bipolar device and the unipolardevice are connected to the output line by means of each individualconnection line.

In the first connection mode, there exists an inductance by theconnection line between the bipolar device and the unipolar device, andthere exists an inductance by the connection line between the unipolardevice and the output line. Therefore, the inductance between theunipolar device and the output line is smaller than the inductancebetween the bipolar device and the output line. In the first connectionmode, when an electric current flows through the unipolar device, acounter electromotive force is generated by the inductance between theunipolar device and the output line. However, the bipolar device isconnected to the unipolar device, and therefore merely a voltageequivalent to the operating voltage of the unipolar device (i.e.,equivalent to a forward voltage in a Schottky barrier diode) is appliedto the bipolar device. The operating voltage of the bipolar device islower than the operating voltage of the unipolar device, and thereforethe current does not flow through the bipolar device. Therefore, acrystal defect area can be restrained from expanding even if the crystaldefect area exists in the bipolar device.

Likewise, in the second connection mode, when an electric current flowsthrough the unipolar device, a counter electromotive force is generatedby an inductance by the connection line between the unipolar device andthe output line. However, the inductance by the connection line betweenthe unipolar device and the output line is smaller than the inductancebetween the bipolar device and the output line, and therefore thecounter electromotive force generated by the smaller inductance betweenthe unipolar device and the output line is absorbed by the greaterinductance between the bipolar device and the output line. Therefore,the current does not flow through the bipolar device. Therefore, acrystal defect area can be restrained from expanding even if the crystaldefect area exists in the bipolar device.

In one embodiment of the present invention, the bipolar device is an SiCsemiconductor device made of a semiconducting material that chieflyincludes SiC. The SiC semiconductor device has a crystal defect that iscalled. “BPD (Basal Plane Dislocation),” and therefore, if a forwardcurrent flows through the PN junction part, BPD will expand, and astacking fault will be caused. In this arrangement, if an electriccurrent flows through the unipolar device, the current can be restrainedfrom flowing through the SiC semiconductor device (i.e., PN junctionpart) that is a bipolar device. As a result, BPD that exists in the SiCsemiconductor device can be restrained from expanding.

In one embodiment of the present invention, a counter electromotiveforce generated by the inductance between the unipolar device and theoutput line is 2.0 V or more. It is conceivable that the operatingvoltage of the bipolar device (for example, the forward voltage of thePN junction diode) is about 2.0 V. Therefore, if the counterelectromotive force generated by the inductance between the unipolardevice and the output line is less than 2.0 V, an electric current doesnot flow through the bipolar device in actual fact. Therefore, if theelectromotive force generated by the inductance between the unipolardevice and the output line is 2.0 V or more, a substantial effect of thepresent invention can be obtained.

In one embodiment of the present invention, the bipolar device includesa PN junction diode, and the unipolar device includes a Schottky barrierdiode.

When an electric current flows through the Schottky barrier diode, acounter electromotive force is generated by an inductance between theSchottky barrier diode and the output line. In the first connection modementioned above, the PN junction diode is connected to the Schottkybarrier diode, and therefore only a voltage equivalent to the forwardvoltage of the Schottky barrier diode is applied to the PN junctiondiode. The forward voltage of the PN junction diode is lower than theforward voltage of the Schottky barrier diode, and therefore the currentdoes not flow through the PN junction diode.

In the second connection mode, the inductance between the Schottkybarrier diode and the output line is smaller than the inductance betweenthe PN junction diode and the output line. Therefore, a counterelectromotive force generated by the inductance between the Schottkybarrier diode and the output line is absorbed by the inductance betweenthe PN junction diode and the output line. Therefore, the current doesnot flow through the PN junction diode.

In one embodiment of the present invention, the electronic circuitfurther includes a connection metal member through which an anode of thePN junction diode is connected to an anode of the Schottky barrier diodeand that is parasitized by an inductance, and the anode of the Schottkybarrier diode is connected to the output line. The connection metalmember may be a wire, a ribbon, or a frame.

When an electric current flows through the Schottky barrier diode, acounter electromotive force is generated by an inductance between theSchottky barrier diode and the output line. However, the anode of the PNjunction diode is connected to the anode of the Schottky barrier diodeby means of the connection metal member, and therefore only a voltageequivalent to the forward voltage of the Schottky barrier diode isapplied to the PN junction diode. The forward voltage of the Schottkybarrier diode is lower than the forward voltage of the PN junctiondiode, and therefore the current does not flow through the PN junctiondiode.

In one embodiment of the present invention, the electronic circuitfurther includes a connection metal member through which a cathode ofthe PN junction diode is connected to a cathode of the Schottky barrierdiode and that is parasitized by an inductance, and die cathode of theSchottky barrier diode is connected to the output line.

When an electric current flows through the Schottky barrier diode, acounter electromotive force is generated by an inductance between theSchottky barrier diode and die output line. However, the cathode of thePN junction diode is connected to the cathode of the Schottky barrierdiode by means of the connection metal member, and therefore only avoltage equivalent to the forward voltage of the Schottky barrier diodeis applied to the PN junction diode. The forward voltage of the Schottkybarrier diode is lower than the forward voltage of the PN junctiondiode, and therefore the current does not flow through the PN junctiondiode.

In one embodiment of the present invention, the PN junction diode isconnected in inverse parallel to a switching device.

In one embodiment of the present invention, the switching device is aMOSFET, and the PN junction diode is built in the MOSFET. In thisarrangement, an electric current can be restrained from flowing throughthe PN junction diode built in the MOSFET, and therefore a forwarddirection deterioration of the MOSFET can be prevented.

In one embodiment of the present invention, the electronic circuitfurther includes a connection metal member through which a source of theMOSFET is connected to the anode of the Schottky barrier diode and thatis parasitized by an inductance, and the anode of the Schottky barrierdiode is connected to the output line.

When an electric current flows through the Schottky barrier diode, acounter electromotive force is generated by an inductance between theSchottky barrier diode and the output line. However, the source of theMOSFET is connected to the anode of the Schottky barrier diode by meansof the connection metal member, and therefore only a voltage equivalentto the operating voltage of the Schottky barrier diode is applied to thePN junction diode built in the MOSFET. The forward voltage of theSchottky barrier diode is lower than the forward voltage of the PNjunction diode, and therefore the current does not flow through the PNjunction diode. Therefore, a forward direction deterioration of theMOSFET can be prevented.

The electronic circuit may further include a connection metal memberthrough which the anode of the Schottky barrier diode is connected tothe output line and that is parasitized by an inductance. Additionally,the connection metal member through which the source of the MOSFET isconnected to the anode of the Schottky barrier diode and the connectionmetal member through which the anode of the Schottky barrier diode isconnected to the output line may be continuously connected together.

In one embodiment of the present invention, the electronic circuitfurther includes a connection metal member through which a drain of theMOSFET is connected to the cathode of the Schottky barrier diode andthat is parasitized by an inductance, and the cathode of the Schottkybarrier diode is connected to the output line.

When an electric current flows through the Schottky barrier diode, acounter electromotive force is generated by an inductance between theSchottky barrier diode and the output line. However, the drain of theMOSFET is connected to the cathode of the Schottky barrier diode bymeans of the connection metal member, and therefore only a voltageequivalent to the forward voltage of the Schottky barrier diode isapplied to the PN junction diode built in the MOSFET. The forwardvoltage of the Schottky barrier diode is lower than the forward voltageof the PN junction diode, and therefore the current does not flowthrough the PN junction diode. Therefore, a forward directiondeterioration of the MOSFET can be prevented.

In one embodiment of the present invention, the connection metal memberincludes a wire. A ribbon and a frame can be mentioned as other examplesof the connection metal member. The wire is a linear connection member,and the ribbon is a belt-like connection member. Generally, thesemembers are metallic members that are flexible. The frame is aplate-like metallic member that is less flexible.

Embodiments of the present invention will be hereinafter described indetail with reference to the accompanying drawings.

FIG. 1 is an electric circuit diagram showing an inverter circuit 1according to a first embodiment of the present invention.

The inverter circuit 1 includes a first module 2 and a second module 3.The first module 2 is composed of a first power source terminal 41, asecond power source terminal 43, two gate terminals 44 and 45, and anoutput terminal 42. The second module 3 is composed of a first powersource terminal 46, a second power source terminal 48, two gateterminals 49 and 50, and an output terminal 47. The first power sourceterminals 41 and 46 of the modules 2 and 3 are connected to a positiveelectrode terminal of a power source (DC power source) 15 through afirst output line 17. An inductive load 16 is disposed between theoutput terminals 42 and 47 of the modules 2 and 3, and is connected tothe output terminals 42 and 47 through a second output line 18. Thesecond power source terminals 43 and 48 of the modules 2 and 3 areconnected to a negative electrode terminal of the power source 15through a third output line 19. A control unit (not shown) is connectedto the gate terminals 44, 45, and 49, 50 of the modules 2 and 3,respectively.

The first module 2 includes a first high-side MOSFET 11 and a secondlow-side MOSFET 12 that is connected in series to the first MOSFET 11.The MOSFETs 11 and 12 have a first PN junction diode (body diode) 11 abuilt in and a second PN junction diode 12 a built in, respectively.Each of these PN junction diodes 11 a and 12 a is a bipolar device. Ananode of each of the PN junction diodes 11 a and 12 a is electricallyconnected to a corresponding source of each of the MOSFETs 11 and 12,whereas a cathode thereof is electrically connected to a correspondingdrain of each of the MOSFETs 11 and 12.

A first Schottky barrier diode 21 that is a unipolar device and a secondSchottky barrier diode 22 that is a unipolar device are connected inparallel to the MOSFETs 11 and 12, respectively. In other words,Schottky barrier diodes 21 and 22 each of which is a unipolar device areconnected in parallel to the PN junction diodes 11 a and 12 a each ofwhich is a bipolar device.

The drain of the first MOSFET 11 is connected to the first power sourceterminal 41 of the first module 2. The cathode of the first Schottkybarrier diode 21 is connected to the drain of the first MOSFET 11 (i.e.,to the cathode of the first PN junction diode 11 a). The source of thefirst MOSFET 11 (i.e., the anode of the first PN junction diode 11 a) isconnected to the anode of the first Schottky barrier diode 21 through aconnection metal member 31. The anode of the first Schottky barrierdiode 21 is connected to the output terminal 42 of the first module 2through another connection metal member 32. In other words, the anode ofthe first Schottky barrier diode 21 is connected to the second outputline 18 through the connection metal member 32.

Inductances L1 and L2 (L1>0, L2>0) parasitize the connection metalmembers 31 and 32, respectively. Therefore, the inductance (L1+L2)between the first PN junction diode 11 a and the second output line 18is greater than the inductance L2 between the first Schottky barrierdiode 21 and the second output line 18.

The drain of the second MOSFET 12 is connected to the output terminal 42of the first module 2. The cathode of the second. Schottky barrier diode22 is connected to the drain of the second. MOSFET 12 (i.e., to thecathode of the second PN junction diode 12 a). The source of the secondMOSFET 12 (i.e., the anode of the second PN junction diode 12 a) isconnected to the anode of the second Schottky barrier diode 22 throughthe connection metal member 33. The anode of the second Schottky barrierdiode 22 is connected to the second power source terminal 43 of thefirst module 2 through the connection metal member 34. In other words,the anode of the second Schottky barrier diode 22 is connected to thethird output line 19 through the connection metal member 34.

Inductances L3 and L4 (L3>0, L4>0) parasitize the connection metalmembers 33 and 34, respectively. Therefore, the inductance (L3+L4)between the second PN junction diode 12 a and the third output line 19is greater than the inductance L4 between the second Schottky barrierdiode 22 and the third output line 19.

The second module 3 includes a third high-side MOSFET 13 and a fourthlow-side MOSFET 14 that is connected in series to the third MOSFET 13.The MOSFETs 13 and 14 have third and fourth PN junction diodes 13 a and14 a (body diodes) built in, respectively. Each of these PN junctiondiodes 13 a and 14 a is a bipolar device. An anode of each of the PNjunction diodes 13 a and 14 a is electrically connected to acorresponding source of each of the MOSFETs 13 and 14, whereas a cathodethereof is electrically connected to a corresponding drain of each ofthe MOSFETs 13 and 14.

Third and fourth Schottky barrier diodes 23 and 24 are connected inparallel to the MOSFETs 13 and 14, respectively. In other words,Schottky barrier diodes 23 and 24 each of which is a unipolar device areconnected in parallel to the PN junction diodes 13 a and 14 a each ofwhich is a bipolar device.

The drain of the third MOSFET 13 is connected to the first power sourceterminal 46 of the second module 3. The cathode of the third Schottkybarrier diode 23 is connected to the drain of the third MOSFET 13 (i.e.,to the cathode of the third PN junction diode 13 a). The source of thethird MOSFET 13 (i.e., the anode of the third PN junction diode 13 a) isconnected to the anode of the third Schottky barrier diode 23 through aconnection metal member 35. The anode of the third. Schottky barrierdiode 23 is connected to the output terminal 47 of the second module 3through another connection metal member 36. In other words, the anode ofthe third Schottky barrier diode 23 is connected to the second outputline 18 through the connection metal member 36.

Inductances L5 and L6 (L5>0, L6>0) parasitize the connection metalmembers 35 and 36, respectively. Therefore, the inductance (L5+L6)between the third PN junction diode 13 a and the second output line 18is greater than the inductance L6 between the third Schottky barrierdiode 23 and the second output line 18.

The drain of the fourth. MOSFET 14 is connected to the output terminal47 of the second module 3. The cathode of the fourth Schottky barrierdiode 24 is connected to the drain of the fourth MOSFET 14 (i.e., to thecathode of the fourth PN junction diode 14 a). The source of the fourthMOSFET 14 (i.e., the anode of the fourth PN junction diode 14 a) isconnected to the anode of the fourth Schottky barrier diode 24 throughthe connection metal member 37. The anode of the fourth Schottky barrierdiode 24 is connected to the second power source terminal 48 of thesecond module 3 through the connection metal member 38. In other words,the anode of the fourth Schottky barrier diode 24 is connected to thethird output line 19 through the connection metal member 38.

Inductances L7 and L8 (L7>0, L8>0) parasitize the connection metalmembers 37 and 38, respectively. Therefore, the inductance (L7+L8)between the fourth PN junction diode 14 a and the third output line 19is greater than the inductance L8 between the fourth Schottky barrierdiode 24 and the third output, line 19.

Each of the first to fourth MOSFETs 11 to 14 is, for example, an SiCdevice in which SiC (silicon carbide) that is an example of a compoundsemiconductor is used as a semiconducting material. The forward voltageVf1 of each of the Schottky barrier diodes 21 to 24 is lower than theforward voltage Vf2 of each of the PN junction diodes 11 a to 14 a. Theforward voltage Vf2 of each of the PN junction diodes 11 a to 14 a is,for example, 2.0 V. On the other hand, the forward voltage Vf1 of eachof the Schottky barrier diodes 21 to 24 is, for example, 1.0 V.

FIG. 2 is a schematic plan view showing an internal structure of themodule 2 of FIG. 1. FIG. 3 is a schematic side view showing an internalstructure of a package 4 of FIG. 2.

The module 2 includes an insulating substrate 8, two packages 4 and 5fixed onto the insulating substrate 8, and a case (not shown) that isfixed to one surface of the insulating substrate 8 and that contains thetwo packages 4 and 5. The insulating substrate 8 has the shape of arectangle when viewed planarly. Each of the packages 4 and 5 is formedin a substantially rectangular shape when viewed planarly. The twopackages 4 and 5 are arranged side by side in the longitudinal directionof the insulating substrate 8.

Referring to FIG. 2 and FIG. 3, the package 4 includes a die pad 51, agate lead 52, a source lead 53, the first MOSFET 11, the first Schottkybarrier diode 21, and a molding resin 57 by which these components aresealed up. The die pad 51 has the shape of the capital letter T whenviewed planarly, and has a rectangular body part and a lead part thatprotrudes substantially from the center of one side of the body part. Aforward end of the lead part protrudes from the molding resin 57. Thegate lead 52 and the source lead 53 are disposed in parallel with thelead part of the die pad 51 with the lead part of the die pad 51therebetween. An end of each of the gate lead 52 and the source lead 53protrudes from the molding resin 57. Each of the die pad 51, the gatelead 52, and the source lead 53 has the shape of a plate made of, forexample, copper or aluminum.

The first MOSFET 11 and the first Schottky barrier diode 21 are arrangedside by side on a surface of the body part of the die pad 51 along oneside of the body part. The first MOSFET 11 and the first Schottkybarrier diode 21 are mounted on one surface of the die pad 51 by diebonding. The first MOSFET 11 has a drain electrode 11 _(D) on itssurface that faces the die pad, and this drain electrode 11 _(D) isjoined to the die pad 51 by means of a conductive solder material. Thefirst MOSFET 11 has a source electrode 11 _(S) and a gate electrode 11_(G) on its surface that is on the side opposite to the die pad 51.

The first Schottky barrier diode 21 has a cathode electrode 21 _(K) onits surface that faces the die pad 51, and this cathode electrode 21_(K) is joined to the die pad 51 by means of a conductive soldermaterial. The first Schottky barrier diode 21 has an anode electrode 21_(A) on its surface that is on the side opposite to the die pad 51.

The gate electrode 11 _(G) of the first MOSFET 11 is electricallyconnected to the gate lead 52 by means of a bonding wire (i.e., aconnection metal member) 39. The source electrode 11 _(S) of the firstMOSFET 11 is electrically connected to the anode electrode 21 _(A) ofthe first Schottky barrier diode 21 by means of the bonding wire (i.e.,the connection metal member) 31. The anode electrode 21 _(A) of thefirst Schottky barrier diode 21 is electrically connected to the sourcelead 53 by means of the bonding wire (i.e., the connection metal member)32.

Wire bonding in which the source electrode 11 _(S) of the first MOSFET11 is connected to the anode electrode 21 _(A) of the first Schottkybarrier diode 21 and wire bonding in which the anode electrode 21 _(A)of the first Schottky barrier diode 21 is connected to the source lead53 may be performed according to a stitch bonding method. In otherwords, it is permissible to perform the connection of the components toeach other according to stitch bonding in which either one of the sourcelead 53 and the source electrode 11 _(S) of the first MOSFET 11 is usedas a starting point, and the remaining one thereof is used as a terminalpoint, and the anode electrode 21 _(A) of the first Schottky barrierdiode 21 is used as a relay point. The bonding wires 31, 32, and 39 arewires made chiefly of, for example, Al, Au, or Cu.

Referring to FIG. 2, the other package 5 includes a die pad 54, a gatelead 55, a source lead 56, the second MOSFET 12, the second Schottkybarrier diode 22, and a molding resin 58 by which these components aresealed up. The die pad 54 has the shape of the capital letter T whenviewed planarly, and has a rectangular body part and a lead part thatprotrudes substantially from the center of one side of the body part. Aforward end of the lead part protrudes from the molding resin 58. Thegate lead 55 and the source lead 56 are disposed in parallel with thelead part of the die pad 54 with the lead part of the die pad 54therebetween. An end of each of the gate lead 55 and the source lead 56protrudes from the molding resin 58. Each of the die pad 54, the gatelead 55, and the source lead 56 has the shape of a plate made of, forexample, copper or aluminum.

The second MOSFET 12 and the second Schottky barrier diode 22 arearranged side by side on a surface of the body part of the die pad 54along one side of the body part. The second MOSFET 12 and the secondSchottky barrier diode 22 are mounted on one surface of the die pad 54by die bonding. The second MOSFET 12 has a drain electrode on itssurface that faces the die pad 54, and this drain electrode is joined tothe die pad 54 by means of a conductive solder material. The secondMOSFET 12 has a source electrode 12 _(S) and a gate electrode 12 _(G) onits surface that is on the side opposite to the die pad 54.

The second Schottky barrier diode 22 has a cathode electrode on itssurface that faces the die pad 54, and this cathode electrode is joinedto the die pad 54 by means of a conductive solder material. The secondSchottky barrier diode 22 has an anode electrode 22 _(A) on its surfacethat is on the side opposite to the die pad 54.

The gate electrode 12 _(G) of the second MOSFET 12 is electricallyconnected to the gate lead 55 by means of a bonding wire (i.e., aconnection metal member) 40. The source electrode 12 _(S) of the secondMOSFET 12 is electrically connected to the anode electrode 22 _(A) ofthe second Schottky barrier diode 22 by means of the bonding wire (i.e.,the connection metal member) 33. The anode electrode 22 _(A) of thesecond Schottky barrier diode 22 is electrically connected to the sourcelead 56 by means of the bonding wire (i.e., the connection metal member)34.

Wire bonding in which the source electrode 12 _(S) of the second MOSFET12 is connected to the anode electrode 22 _(A) of the second Schottkybarrier diode 22 and wire bonding in which the anode electrode 22 _(A)of the second Schottky barrier diode 22 is connected to the source lead56 may be performed according to a stitch bonding method. In otherwords, it is permissible to perform the connection of the components toeach other according to stitch bonding in which either one of the sourcelead 56 and the source electrode 12 _(S) of the second MOSFET 11 is usedas a starting point, and the remaining one thereof is used as a terminalpoint, and the anode electrode 22 _(A) of the second Schottky barrierdiode 22 is used as a relay point. The bonding wires 33, 34, and 40 arewires made chiefly of, for example, Al, Au, or Cu.

The source lead 56 of the package 4 and the lead part of the die pad 54of the package 5 are electrically connected together by means of abelt-like metallic pattern 59 having the shape of the capital letter Uwhen viewed planarly. The metallic pattern 59 is a thin film wire madeof, for example, copper or aluminum, and is formed on a surface of theinsulating substrate 8.

The gate lead 52 of the package 4 is connected to the gate terminal 44.The gate terminal 44 is drawn out of the case of the module 2. The leadpart of the die pad 51 of the package 4 is connected to the first powersource terminal 41. The first power source terminal 41 is drawn out ofthe case of the module 2. The power source 15 is connected to the firstpower source terminal 41. The metallic pattern 59 is connected to theoutput terminal 42. The output terminal 42 is drawn out of the case ofthe module 2.

The gate lead 55 of the package 5 is connected to the gate terminal 45.The gate terminal 45 is drawn out of the case of the module 2. Thesource lead 56 of the package 5 is connected to the second power sourceterminal 43. The second power source terminal 43 is drawn out of thecase of the module 2. The second power source terminal 43 is grounded(i.e., is connected to a negative electrode of the power source 15).

The internal structure of the second module 3 is the same as theinternal structure of the first module 2, and therefore a description ofits structure is omitted.

Referring back to FIG. 1, in the thus formed inverter circuit 1, thefirst MOSFET 11 and the fourth MOSFET 14 are turned on, for example.Thereafter, the MOSFETs 11 and 14 are turned off, and, as a result, allof the MOSFETs 11 to 14 are brought into an OFF state. When apredetermined dead time period elapses, the second MOSFET 12 and thethird MOSFET 13 are, this time, turned on. Thereafter, the MOSFETs 12and 13 are turned off, and, as a result, all of the MOSFETs 11 to 14 arebrought into an OFF state. When a predetermined dead time periodelapses, the first MOSFET 11 and the fourth MOSFET 14 are turned onagain. This operation is repeatedly performed, and, as a result, theload 16 is driven in an AC manner.

When the first MOSFET 11 and the fourth MOSFET 14 are turned on, anelectric current flows from a positive electrode of the power source 15toward the third output line 19 through the first output line 17, thefirst MOSFET 11, the connection metal member 31, the connection metalmember 32, the second output line 18, the load 16, the second outputline 18, the fourth MOSFET 14, the connection metal member 37, and theconnection metal member 38. In this case, the current flows through theload 16 in a direction shown by arrow “A.”

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 attempts to maintain anelectric current flowing through the load 16 (i.e., maintain the currentflowing in the direction shown by arrow “A”). Therefore, the currentflows through the connection metal wire 34, the second Schottky barrierdiode 22, the load 16, the connection metal wire 36, and the thirdSchottky barrier diode 23 in the direction from the connection metalwire 34 toward the third Schottky barrier diode 23. As a result, thecurrent flows through the connection metal wire 34 and the connectionmetal wire 36.

When the current flows through the connection metal wire 34, a counterelectromotive force is generated by an inductance L4 parasitizing thismetal wire. However, the voltage of this counter electromotive force isnot applied to the second PN junction diode 12 a. The reason is that theanode of the second PN junction diode 12 a is connected to the anode ofthe second Schottky barrier diode 22 by means of the connection metalwire 33. Only a voltage equivalent to the forward voltage Vf1 of thesecond Schottky barrier diode 22 is applied to the second PN junctiondiode 12 a. In other words, the second PN junction diode 12 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the second PN junction diode 12 a.

Likewise, when an electric current flows through the connection metalwire 36, a counter electromotive force is generated by an inductance L6parasitizing this metal wire. However, the voltage of this counterelectromotive force is not applied to the third PN junction diode 13 a.The reason is that the anode of the third PN junction diode 13 a isconnected to the anode of the third Schottky barrier diode 23 by meansof the connection metal wire 35. Only a voltage equivalent to theforward voltage Vf1 of the third Schottky barrier diode 23 is applied tothe third PN junction diode 13 a. In other words, the third PN junctiondiode 13 a does not receive a voltage greater than its forward voltageVf2. Therefore, the current does not flow through the third PN junctiondiode 13 a.

When the second MOSFET 12 and the third MOSFET 13 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, thethird MOSFET 13, the connection metal member 35, the connection metalmember 36, the second output line 18, the load 16, the second outputline 18, the second MOSFET 12, the connection metal member 33, and theconnection metal member 34. In this case, the current flows through theload 16 in a direction shown by arrow B.

When all of the MOSFETs 11 to 14 are brought into an OFF state in thisstate, the inductance of the inductive load 16 attempts to maintain anelectric current flowing through the load 16 (i.e., maintain the currentflowing in the direction shown by arrow B). Therefore, the current flowsthrough the connection metal wire 38, the fourth Schottky barrier diode24, the load 16, the connection metal wire 32, and the first Schottkybarrier diode 21 in the direction from the connection metal wire 38toward the first Schottky barrier diode 21. As a result, the currentflows through the connection metal wire 38 and the connection metal wire32.

When the current flows through the connection metal wire 38, anelectromotive force is generated by an inductance L8 parasitizing thismetal wire. However, the voltage of this counter electromotive force isnot applied to the fourth PN junction diode 14 a. The reason is that theanode of the fourth PN junction diode 14 a is connected to the anode ofthe fourth Schottky barrier diode 24 by means of the connection metalwire 37. Only a voltage equivalent to the forward voltage Vf1 of thefourth Schottky barrier diode 24 is applied to the fourth PN junctiondiode 14 a. In other words, the fourth PN junction diode 14 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the fourth PN junction diode 14 a.

Likewise, when the current flows through the connection metal wire 32,an electromotive force is generated by an inductance L2 parasitizingthis metal wire. However, the voltage of this counter electromotiveforce is not applied to the first PN junction diode 11 a. The reason isthat the anode of the first PN junction diode 11 a is connected to theanode of the first Schottky barrier diode 21 by means of the connectionmetal wire 31. Only a voltage equivalent to the forward voltage Vf1 ofthe first Schottky barrier diode 21 is applied to the first PN junctiondiode 11 a. In other words, the first PN junction diode 11 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the first PN junction diode 11 a.

As described above, in the first embodiment, an electric current can berestrained from flowing through the PN junction diodes 11 a to 14 abuilt in the MOSFETs 11 to 14, respectively, during a dead time period.Therefore, a forward direction deterioration of the MOSFETs 11 to 14 canbe prevented.

FIG. 4 is an electric circuit diagram showing an inverter circuit 1Aaccording to a second embodiment of the present invention. In FIG. 4,the same reference numeral as in FIG. 1 is given to a componentcorresponding to each component shown in FIG. 1.

In the first embodiment mentioned above, the drain electrode of each ofthe MOSFETs 11 to 14 and the cathode electrode of each of the Schottkybarrier diodes 21 to 24 are joined to the die pad in each package as inthe package 4 of FIG. 3. On the other hand, in the second embodiment,the source electrode of each of the MOSFETs 11 to 14 and the anodeelectrode of each of the Schottky barrier diodes 21 to 24 are joined tothe die pad in each package. Therefore, in each package, the drainelectrode is formed on a surface of each of the MOSFETs 11 to 14 that ison the side opposite to the die pad, and the cathode electrode is formedon a surface of each of the Schottky barrier diodes 21 to 24 that is onthe side opposite to the die pad.

Referring to FIG. 4, the source of the first MOSFET 11 (i.e., the anodeof the first PN junction diode 11 a) and the anode of the first Schottkybarrier diode 21 are connected to an output terminal 42 of a firstmodule 2A. The drain of the first MOSFET 11 (i.e., the cathode of thefirst PN junction diode 11 a) is connected to the cathode of the firstSchottky barrier diode 21 by means of a connection metal member 31Aparasitized by an inductance L1. The cathode of the first Schottkybarrier diode 21 is connected to a first power source terminal 41 of thefirst module 2A by means of a connection metal member 32A parasitized byan inductance L2. In other words, the cathode of the first Schottkybarrier diode 21 is connected to the first output line 17 through theconnection metal member 32A parasitized by the inductance L2.

The source of the second MOSFET 12 (i.e., the anode of the second PNjunction diode 12 a) and the anode of the second Schottky barrier diode22 are connected to a second power source terminal 43 of the firstmodule 2A. The drain of the second MOSFET 12 (i.e., the cathode of thesecond PN junction diode 12 a) is connected to the cathode of the secondSchottky barrier diode 22 by means of a connection metal member 33Aparasitized by an inductance L3. The cathode of the second Schottkybarrier diode 22 is connected to the output terminal 42 of the firstmodule 2A by means of a connection metal member 34A parasitized by aninductance L4. In other words, the cathode of the second Schottkybarrier diode 22 is connected to the second output line 18 through theconnection metal member 34A parasitized by the inductance L4.

The source of the third MOSFET 13 (i.e., the anode of the third PNjunction diode 13 a) and the anode of the third Schottky barrier diode23 are connected to an output terminal 47 of a second module 3A. Thedrain of the third MOSFET 13 (i.e., the cathode of the third PN junctiondiode 13 a) is connected to the cathode of the third Schottky barrierdiode 23 by means of a connection metal member 35A parasitized by aninductance L5. The cathode of the third Schottky barrier diode 23 isconnected to a first power source terminal 46 of the second module 3A bymeans of a connection metal member 36A parasitized by an inductance L6.In other words, the cathode of the third Schottky barrier diode 23 isconnected to the first output line 17 through the connection metalmember 36A parasitized by the inductance L6.

The source of the fourth MOSFET 14 (i.e., the anode of the fourth PNjunction diode 14 a) and the anode of the fourth Schottky barrier diode24 are connected to a second power source terminal 48 of the secondmodule 3A. The drain of the fourth MOSFET 14 (i.e., the cathode of thefourth PN junction diode 14 a) is connected to the cathode of the fourthSchottky barrier diode 24 by means of a connection metal member 37Aparasitized by an inductance L7. The cathode of the fourth Schottkybarrier diode 24 is connected to the output terminal 47 of the secondmodule 3A by means of a connection metal member 38A parasitized by aninductance L8. In other words, the cathode of the fourth Schottkybarrier diode 24 is connected to the second output line 18 through theconnection metal member 38A parasitized by the inductance L8.

Although the reference numeral that designates the inductance is, forconvenience, set to be the same as that of the first embodiment, thisdoes not mean that the inductances of the connection metal members 31Ato 38A are respectively equal to the inductances of the connection metalmembers 31 to 38 mentioned in the first embodiment.

When the first MOSFET 11 and the fourth MOSFET 14 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, theconnection metal member 32A, the connection metal member 31A, the firstMOSFET 11, the second output line 18, the load 16, the second outputline 18, the connection metal member 38A, the connection metal member37A, and the fourth MOSFET 14. In this case, the current flows throughthe load 16 in the direction shown by arrow “A.”

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow “A”). Therefore, the current flowsthrough the second Schottky barrier diode 22, the connection metal wire34A, the load 16, the third Schottky barrier diode 23, and theconnection metal wire 36A in the direction from the second Schottkybarrier diode 22 toward the connection metal wire 36A. As a result, thecurrent flows through the connection metal wire 34A and the connectionmetal wire 36A.

When the current flows through the connection metal wire 34A, a counterelectromotive force is generated by the inductance L4 parasitizing thismetal wire. However, the voltage of this counter electromotive force isnot applied to the second PN junction diode 12 a. The reason is that thecathode of the second PN junction diode 12 a is connected to the cathodeof the second Schottky barrier diode 22 by means of the connection metalwire 33A. Only a voltage equivalent to the forward voltage Vf1 of thesecond Schottky barrier diode 22 is applied to the second PN junctiondiode 12 a. In other words, the second PN junction diode 12 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the second PN junction diode 12 a.

Likewise, when an electric current flows through the connection metalwire 36A, a counter electromotive force is generated by the inductanceL6 parasitizing this metal wire. However, the voltage of this counterelectromotive force is not applied to the third PN junction diode 13 a.The reason is that the cathode of the third PN junction diode 13 a isconnected to the cathode of the third Schottky barrier diode 23 by meansof the connection metal wire 35A. Only a voltage equivalent to theforward voltage Vf1 of the third Schottky barrier diode 23 is applied tothe third PN junction diode 13 a. In other words, the third PN junctiondiode 13 a does not receive a voltage greater than its forward voltageVf2. Therefore, the current does not flow through the third PN junctiondiode 13 a.

When the second MOSFET 12 and the third MOSFET 13 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, theconnection metal member 36A, the connection metal member 35A, the thirdMOSFET 13, the second output line 18, the load 16, the second outputline 18, the connection metal member 34A, the connection metal member33A, and the second MOSFET 12. In this case, the current flows throughthe load 16 in the direction shown by arrow B.

When all of the MOSFETs 11 to 14 are brought into an OFF state in thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow B). Therefore, the current flows throughthe fourth Schottky barrier diode 24, the connection metal wire 38A, theload 16, the first Schottky barrier diode 21, and the connection metalwire 32A in the direction from the fourth Schottky barrier diode 24toward the connection metal wire 32A. As a result, the current flowsthrough the connection metal wire 38A and the connection metal wire 32A.

When the current flows through the connection metal wire 38A, a counterelectromotive force is generated by the inductance L8 parasitizing thismetal wire. However, the voltage of this counter electromotive force isnot applied to the fourth PN junction diode 14 a. The reason is that thecathode of the fourth PN junction diode 14 a is connected to the cathodeof the fourth Schottky barrier diode 24 by means of the connection metalwire 37A. Only a voltage equivalent to the forward voltage Vf1 of thefourth Schottky barrier diode 24 is applied to the fourth PN junctiondiode 14 a. In other words, the fourth PN junction diode 14 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the fourth PN junction diode 14 a.

Likewise, when the current flows through the connection metal wire 32A,a counter electromotive force is generated by the inductance L2parasitizing this metal wire. However, the voltage of this counterelectromotive force is not applied to the first PN junction diode 11 a.The reason is that the cathode of the first PN junction diode 11 a isconnected to the cathode of the first Schottky barrier diode 21 by meansof the connection metal wire 31A. Only a voltage equivalent to theforward voltage Vf1 of the first Schottky barrier diode 21 is applied tothe first PN junction diode 11 a. In other words, the first PN junctiondiode 11 a does not receive a voltage greater than its forward voltageVf2. Therefore, the current does not flow through the first PN junctiondiode 11 a.

As described above, in the second embodiment, an electric current can berestrained from flowing through the PN junction diodes 11 a to 14 abuilt in the MOSFETs 11 to 14, respectively, during a dead time periodin the same way as in the first embodiment. Therefore, a forwarddirection deterioration of the MOSFETs 11 to 14 can be prevented.

FIG. 5 is an electric circuit diagram showing an inverter circuit 1Baccording to a third embodiment of the present invention. In FIG. 5, thesame reference numeral as in FIG. 1 is given to a componentcorresponding to each component shown in FIG. 1.

In the first embodiment mentioned above, each source of the MOSFETs 11to 14 (each anode of the PN junction diodes 11 a to 14 a) is connectedto each corresponding anode of the Schottky barrier diodes 21 to 24through the connection metal members 31, 33, 35, and 37, respectively.

On the other hand, in the third embodiment, each source of the MOSFETs11 to 14 (each anode of the PN junction diodes 11 a to 14 a) isconnected to an output line through connection metal members 31B, 33B,35B, and 37B parasitized by the inductances L1, L3, L5, and L7,respectively. Herein, the reference numeral that designates theinductance is set to be the same as that of the first embodiment merelyfor convenience, and this does not mean that the inductances of theconnection metal members 31B to 38B are respectively equal to theinductances of the connection metal members 31 to 38 mentioned in thefirst embodiment.

The detailed structure is as follows. The source of the first MOSFET 11(i.e., the anode of the first PN junction diode 11 a) is connected tothe output terminal 42 of the first module 2B through the connectionmetal member 31B. In other words, the source of the first MOSFET 11(i.e., the anode of the first PN junction diode 11 a) is connected tothe second output line 18 through the connection metal member 31B.

The source of the second MOSFET 12 (i.e., the anode of the second PNjunction diode 12 a) is connected to the second power source terminal 43of the first module 2B through the connection metal member 33B. In otherwords, the source of the second MOSFET 12 (i.e., the anode of the secondPN junction diode 12 a) is connected to the third output line 19 throughthe connection metal member 33B.

The source of the third MOSFET 13 (i.e., the anode of the third PNjunction diode 13 a) is connected to the output terminal 47 of thesecond module 3B through the connection metal member 35B. In otherwords, the source of the third MOSFET 13 (i.e., the anode of the thirdPN junction diode 13 a) is connected to the second output line 18through the connection metal member 35B.

The source of the fourth MOSFET 14 (i.e., the anode of the fourth PNjunction diode 14 a) is connected to the second power source terminal 48of the second module 3B through the connection metal member 37B. Inother words, the source of the fourth MOSFET 14 (i.e., the anode of thefourth PN junction diode 14 a) is connected to the third output line 19through the connection metal member 37B.

As in the first embodiment, the anodes of the first and third Schottkybarrier diodes 21 and 23 are connected to the second output line 18through the connection metal members 32B and 36B parasitized by theinductances L2 and L6, respectively. As in the first embodiment, theanodes of the second and fourth Schottky barrier diodes 22 and 24 areconnected to the third output line 19 through the connection metalmembers 34B and 38B parasitized by the inductances L4 and L8,respectively.

In the third embodiment, the inductances L1, L3, L5, and L7 parasitizingthe connection metal members 31B, 33B, 35B, and 37B are set to begreater than the inductances L2, L4, L6, and L8 parasitizing theconnection metal members 32B, 34B, 36B, and 38B, respectively. In otherwords, the relations L1>L2, L3>L4, L5>L6, and L7>L8 are established. Forexample, if each of the connection metal members 31B to 38B is a bondingwire, the inductances L1 to L8 can be adjusted by adjusting the lengthof the bonding wire, the diameter of the bonding wire, the loop angle ofthe bonding wire, etc. The inductance becomes greater in proportion toan increase in the length of the bonding wire, in proportion to adecrease in the diameter of the bonding wire, or in proportion to anincrease in the loop angle of the bonding wire.

When the first MOSFET 11 and the fourth MOSFET 14 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, thefirst MOSFET 11, the connection metal member 31B, the second output line18, the load 16, the second output line 18, the fourth MOSFET 14, andthe connection metal member 37B. In this case, the current flows throughthe load 16 in the direction shown by arrow “A.”

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow “A”). Therefore, the current flowsthrough the connection metal wire 34B, the second Schottky barrier diode22, the load 16, the connection metal wire 36B, and the third Schottkybarrier diode 23 in the direction from the connection metal wire 34Btoward the third Schottky barrier diode 23. As a result, the currentflows through the connection metal wire 34B and the connection metalwire 36B.

When the current flows through the connection metal wire 34B, a counterelectromotive force is generated by the inductance L4 parasitizing thismetal wire. The counter electromotive force generated by the inductanceL4 is supplied to the connection metal wire 33B. However, the inductanceL3 parasitizing the connection metal wire 33B is greater than theinductance L4, and therefore the energy of the counter electromotiveforce is absorbed by the inductance L3. Therefore, the second PNjunction diode 12 a does not receive a voltage greater than its forwardvoltage Vf2. Therefore, the current does not flow through the second PNjunction diode 12 a.

Likewise, when the current flows through the connection metal wire 36B,a counter electromotive force is generated by the inductance L6parasitizing this metal wire. The counter electromotive force generatedby the inductance L6 is supplied to the connection metal wire 35B.However, the inductance L5 parasitizing the connection metal wire 35B isgreater than the inductance L6, and therefore the energy of the counterelectromotive force is absorbed by the inductance L5. Therefore, thethird PN junction diode 13 a does not receive a voltage greater than itsforward voltage Vf2. Therefore, the current does not flow through thethird PN junction diode 13 a.

When the second MOSFET 12 and the third MOSFET 13 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, thethird MOSFET 13, the connection metal member 35B, the second output line18, the load 16, the second output line 18, the second MOSFET 12, andthe connection metal member 33B. In this case, the current flows throughthe load 16 in the direction shown by arrow B.

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow B). Therefore, the current flows throughthe connection metal wire 38B, the fourth Schottky barrier diode 24, theload 16, the connection metal wire 32B, and the first Schottky barrierdiode 21 in the direction from the connection metal wire 38B toward thefirst Schottky barrier diode 21. As a result, the current flows throughthe connection metal wire 38B and the connection metal wire 32B.

When the current flows through the connection metal wire 38B, a counterelectromotive force is generated by the inductance L8 parasitizing thismetal wire. The counter electromotive force generated by the inductanceL8 is supplied to the connection metal wire 37B. However, the inductanceL7 parasitizing the connection metal wire 37B is greater than theinductance L8, and therefore the energy of the counter electromotiveforce is absorbed by the inductance L7. Therefore, the fourth PNjunction diode 14 a does not receive a voltage greater than its forwardvoltage Vf2. Therefore, the current does not flow through the fourth PNjunction diode 14 a.

Likewise, when the current flows through the connection metal wire 32B,a counter electromotive force is generated by the inductance L2parasitizing this metal wire. The counter electromotive force generatedby the inductance L2 is supplied to the connection metal wire 31B.However, the inductance L1 parasitizing the connection metal wire 31B isgreater than the inductance L2, and therefore the energy of the counterelectromotive force is absorbed by the inductance L1. Therefore, thefirst PN junction diode 11 a does not receive a voltage greater than itsforward voltage Vf2. Therefore, the current does not flow through thefirst PN junction diode 11 a.

As described above, in the third embodiment, an electric current can berestrained from flowing through the PN junction diodes 11 a to 14 abuilt in the MOSFETs 11 to 14, respectively, during a dead time periodin the same way as in the first embodiment. Therefore, a forwarddirection deterioration of the MOSFETs 11 to 14 can be prevented.

FIG. 6 is an electric circuit diagram showing an inverter circuit 1Caccording to a fourth embodiment of the present invention. In FIG. 6,the same reference numeral as in FIG. 1 is given to a componentcorresponding to each component shown in FIG. 1.

In the first embodiment mentioned above, the drain electrode of each ofthe MOSFETs 11 to 14 and the cathode electrode of each of the Schottkybarrier diodes 21 to 24 are joined to the die pad in each package as inthe package 4 of FIG. 3. On the other hand, in the fourth embodiment,the source electrode of each of the MOSFETs 11 to 14 and the anodeelectrode of each of the Schottky barrier diodes 21 to 24 are joined tothe die pad in each package. Therefore, in each package, the drainelectrode is formed on the surface of each of the MOSFETs 11 to 14 thatis on the side opposite to the die pad, and the cathode electrode isformed on the surface of each of the Schottky barrier diodes 21 to 24that is on the side opposite to the die pad.

Referring to FIG. 6, the source of the first MOSFET 11 (i.e., the anodeof the first PN junction diode 11 a) and the anode of the first Schottkybarrier diode 21 are connected to an output terminal 42 of a firstmodule 2C. The drain of the first MOSFET 11 (i.e., the cathode of thefirst PN junction diode 11 a) is connected to a first power sourceterminal 41 of the first module 2C by means of a connection metal member31C parasitized by the inductance L1. The cathode of the first Schottkybarrier diode 21 is connected to the first power source terminal 41 ofthe first module 2C by means of a connection metal member 32Cparasitized by the inductance L2. In other words, the cathode of thefirst PN junction diode 11 a is connected to the first output line 17through the connection metal member 31C, and the cathode of the firstSchottky barrier diode 21 is connected to the first output line 17through the connection metal member 32C.

The source of the second MOSFET 12 (i.e., the anode of the second PNjunction diode 12 a) and the anode of the second Schottky barrier diode22 are connected to a second power source terminal 43 of the firstmodule 2C. The drain of the second MOSFET 12 (i.e., the cathode of thesecond PN junction diode 12 a) is connected to an output terminal 42 ofthe first module 2C by means of a connection metal member 33Cparasitized by the inductance L3. The cathode of the second Schottkybarrier diode 22 is connected to the output terminal 42 of the firstmodule 2C by means of a connection metal member 34C parasitized by theinductance L4. In other words, the cathode of the second PN junctiondiode 12 a is connected to the second output line 18 through theconnection metal member 33C, and the cathode of the second Schottkybarrier diode 22 is connected to the second output line 18 through theconnection metal member 34C.

The source of the third MOSFET 13 (i.e., the anode of the third PNjunction diode 13 a) and the anode of the third Schottky barrier diode23 are connected to an output terminal 47 of a second module 3C. Thedrain of the third MOSFET 13 (i.e., the cathode of the third PN junctiondiode 13 a) is connected to the first power source terminal 46 of thesecond module 3C by means of a connection metal member 35C parasitizedby the inductance L5. The cathode of the third Schottky barrier diode 23is connected to the first power source terminal 46 of the second module3C by means of a connection metal member 36C parasitized by theinductance L6. In other words, the cathode of the third PN junctiondiode 13 a is connected to the first output line 17 through theconnection metal member 35C, and the cathode of the third Schottkybarrier diode 23 is connected to the first output line 17 through theconnection metal member 36C.

The source of the fourth MOSFET 14 (i.e., the anode of the fourth PNjunction diode 14 a) and the anode of the fourth Schottky barrier diode24 are connected to a second power source terminal 48 of the secondmodule 3C. The drain of the fourth MOSFET 14 (i.e., the cathode of thefourth PN junction diode 14 a) is connected to the output terminal 47 ofthe second module 3C by means of a connection metal member 37Cparasitized by the inductance L7. The cathode of the fourth Schottkybarrier diode 24 is connected to the output terminal 42 of the secondmodule 3C by means of a connection metal member 38C parasitized by theinductance L8. In other words, the cathode of the fourth PN junctiondiode 14 a is connected to the second output line 18 through theconnection metal member 37C, and the cathode of the fourth Schottkybarrier diode 24 is connected to the second output line 18 through theconnection metal member 38C.

Although the reference numeral that designates the inductance is, forconvenience, set to be the same as that of the first embodiment, thisdoes not mean that the inductances of the connection metal members 31Cto 38C are respectively equal to the inductances of the connection metalmembers 31 to 38 mentioned in the first embodiment.

In the fourth embodiment, the inductances L1, L3, L5, and L7parasitizing the connection metal members 31C, 33C, 35C, and 37C are setto be greater than the inductances L2, L4, L6, and L8 parasitizing theconnection metal members 32C, 34C, 36C, and 38C, respectively. In otherwords, the relations L1>L2, L3>L4, L5>L6, and L7>L8 are established. Forexample, if each of the connection metal members 31C to 38C is a bondingwire, the inductances L1 to L8 can be adjusted by adjusting the lengthof the bonding wire, the diameter of the bonding wire, the loop angle ofthe bonding wire, etc.

When the first MOSFET 11 and the fourth MOSFET 14 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, theconnection metal member 31C, the first MOSFET 11, the second output line18, the load 16, the second output line 18, the connection metal member37C, and the fourth MOSFET 14. In this case, the current flows throughthe load 16 in the direction shown by arrow “A.”

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow “A”). Therefore, the current flowsthrough the second Schottky barrier diode 22, the connection metal wire34C, the load 16, the third Schottky barrier diode 23, and theconnection metal wire 36C in the direction from the second Schottkybarrier diode 22 toward the connection metal wire 36C. As a result, thecurrent flows through the connection metal wire 34C and the connectionmetal wire 36C.

When the current flows through the connection metal wire 34C, a counterelectromotive force is generated by the inductance L4 parasitizing thismetal wire. The counter electromotive force generated by the inductanceL4 is supplied to the connection metal wire 33C. However, the inductanceL3 parasitizing the connection metal wire 33C is greater than theinductance L4, and therefore the energy of the counter electromotiveforce is absorbed by the inductance L3. Therefore, the second PNjunction diode 12 a does not receive a voltage greater than its forwardvoltage Vf2. Therefore, the current does not flow through the second PNjunction diode 12 a.

Likewise, when the current flows through the connection metal wire 36C,a counter electromotive force is generated by the inductance L6parasitizing this metal wire. The counter electromotive force generatedby the inductance L6 is supplied to the connection metal wire 35C.However, the inductance L5 parasitizing the connection metal wire 35C isgreater than the inductance L6, and therefore the energy of the counterelectromotive force is absorbed by the inductance L5. Therefore, thethird PN junction diode 13 a does not receive a voltage greater than itsforward voltage Vf2. Therefore, the current does not flow through thethird PN junction diode 13 a.

When the second MOSFET 12 and the third MOSFET 13 are turned on, anelectric current flows from the positive electrode of the power source15 toward the third output line 19 through the first output line 17, theconnection metal member 35C, the third MOSFET 13, the second output line18, the load 16, the second output line 18, the connection metal member33C, and the second MOSFET 12. In this case, the current flows throughthe load 16 in the direction shown by arrow B.

When all of the MOSFETs 11 to 14 are brought into an OFF state from thisstate, the inductance of the inductive load 16 maintains an electriccurrent flowing through the load 16 (i.e., maintains the current flowingin the direction shown by arrow B). Therefore, the current flows throughthe fourth Schottky barrier diode 24, the connection metal wire 38C, theload 16, the first Schottky barrier diode 21, and the connection metalwire 32C in the direction from the fourth Schottky barrier diode 24toward the connection metal wire 32C. As a result, the current flowsthrough the connection metal wire 38C and the connection metal wire 32C.

When the current flows through the connection metal wire 38C, a counterelectromotive force is generated by the inductance L8 parasitizing thismetal wire. The counter electromotive force generated by the inductanceL8 is supplied to the connection metal wire 37C. However, the inductanceL7 parasitizing the connection metal wire 37C is greater than theinductance L8, and therefore the energy of the counter electromotiveforce is absorbed by the inductance L7. Therefore, the fourth PNjunction diode 14 a does not receive a voltage greater than its forwardvoltage Vf2. Therefore, the current does not flow through the fourth PNjunction diode 14 a.

Likewise, when the current flows through the connection metal wire 32C,a counter electromotive force is generated by the inductance L2parasitizing this metal wire. The counter electromotive force generatedby the inductance L2 is supplied to the connection metal wire 31C.However, the inductance L1 parasitizing the connection metal wire 31C isgreater than the inductance L2, and therefore the energy of the counterelectromotive force is absorbed by the inductance L1. Therefore, thefirst PN junction diode 11 a does not receive a voltage greater than itsforward voltage Vf2. Therefore, the current does not flow through thefirst PN junction diode 11 a.

As described above, in the fourth embodiment, an electric current can berestrained from flowing through the PN junction diodes 11 a to 14 abuilt in the MOSFETs 11 to 14, respectively, during a dead time periodin the same way as in the first embodiment. Therefore, a forwarddirection deterioration of the MOSFETs 11 to 14 can be prevented.

FIG. 7 is an electric circuit diagram showing a converter circuit 101 towhich an electronic circuit according to a fifth embodiment of thepresent invention is applied.

This converter circuit 101 is a step-down DC-DC converter circuit. Theconverter circuit 101 includes a module 2, a coil 72, and a capacitor73. The module 2 is the same in structure as the first module 2 of thefirst embodiment. The first power source terminal 41 of the module 2 isconnected to a positive electrode terminal of a power source 115 throughthe first output line 17. The second power source terminal 43 of themodule 2 is connected to a negative electrode terminal of the powersource 115 through the third output line 19. The output terminal 42 ofthe module 2 is connected to a first outside terminal 111 through thesecond output line 18 and the coil 72. The second power source terminal43 of the module 2 is connected to a second outside terminal 112 throughthe third output line 19.

The capacitor 73 is connected to a portion between a connection pointthat is located between the coil 72 and the first outside terminal 111and the third output line 19 that is located between the second powersource terminal 43 and the second outside terminal 112. The coil 72 andthe capacitor 73 form a smoothing circuit. A load 116 is connected to aportion between the first outside terminal 111 and the second outsideterminal 112. The gate terminal 45 of the module 2 is connected to thethird output line 19 through a resistor 71. A control unit (not shown)is connected to the gate terminal 44 of the module 2.

The module 2 includes a first high-side MOSFET 11 and a second low-sideMOSFET 12 that is connected in series to the first MOSFET 11. TheMOSFETs 11 and 12 have a first PN junction diode (body diode) 11 a builtin and a second PN junction diode 12 a built in, respectively. Each ofthese PN junction diodes 11 a and 12 a is a bipolar device.

The first Schottky barrier diode 21 that is a unipolar device and thesecond Schottky barrier diode 22 that is a unipolar device are connectedin parallel to the MOSFETs 11 and 12, respectively. In other words, theSchottky barrier diodes 21 and 22 each of which is a unipolar device areconnected in parallel to the PN junction diodes 11 a and 12 a each ofwhich is a bipolar device.

The drain of the first MOSFET 11 is connected to the first power sourceterminal 41 of the module 2. The cathode of the first Schottky barrierdiode 21 is connected to the drain of the first MOSFET 11 (i.e., to thecathode of the first PN junction diode 11 a). The source of the firstMOSFET 11 (i.e., the anode of the first PN junction diode 11 a) isconnected to the anode of the first Schottky barrier diode 21 throughthe connection metal member 31 parasitized by the inductance L1. Theanode of the first Schottky barrier diode 21 is connected to the outputterminal 42 of the module 2 through the connection metal member 32parasitized by the inductance L2. In other words, the anode of the firstSchottky barrier diode 21 is connected to the second output line 18through the connection metal member 32 parasitized by the inductance L2.

The drain of the second MOSFET 12 is connected to the output terminal 42of the module 2. The cathode of the second Schottky barrier diode 22 isconnected to the drain of the second MOSFET 12 (i.e., to the cathode ofthe second PN junction diode 12 a). The source of the second MOSFET 12(i.e., the anode of the second PN junction diode 12 a) is connected tothe anode of the second Schottky barrier diode 22 through the connectionmetal member 33 parasitized by the inductance L3. The anode of thesecond Schottky barrier diode 22 is connected to the second power sourceterminal 43 of the module 2 through the connection metal member 34parasitized by the inductance L4. In other words, the anode of thesecond Schottky barrier diode 22 is connected to the third output line19 through the connection metal member 34 parasitized by the inductanceL4.

Each of the MOSFETs 11 and 12 is an SiC device in which, for example,SiC (silicon carbide) that is an example of a compound semiconductor isused as a semiconducting material. The forward voltage Vf1 of each ofthe Schottky barrier diodes 21 and 22 is lower than the forward voltageVf2 of each of the PN junction diodes 11 a and 12 a. The forward voltageVf2 of each of the PN junction diodes 11 a and 12 a is, for example, 2.0V. The forward voltage Vf1 of each of the Schottky barrier diodes 21 and22 is, for example, 1.0 V.

In the thus arranged converter circuit 101, the first MOSFET 11 isturned on/off (is switched) at a predetermined duty ratio. When thefirst MOSFET 11 is turned on, an electric current flows from a positiveelectrode of a power source 115 toward a load 116 through the firstoutput line 17, the first MOSFET 11, the connection metal member 31, theconnection metal member 32, the second output line 18, and the coil 72(the smoothing circuit). As a result, energy is stored in the coil 72,and electric power is supplied to the load 116.

When the first MOSFET 11 is turned off, the coil 72 attempts to maintainan electric current flowing therethrough, and generates an electromotiveforce. This electromotive force allows the current to flow through thecoil 72 through the connection metal member 34 and the second Schottkybarrier diode 22, and electric power is supplied to the load 116. Thisoperation is repeatedly performed, and, as a result, a voltage lowerthan the voltage of the power source 115 is applied to the load 116.

As described above, when the first MOSFET 11 is changed from an ON stateto an OFF state, an electric current flows through the connection metalmember 34 by an electromotive force generated by the coil 72. When thecurrent flows through the connection metal member 34, a counterelectromotive force is generated by the inductance L4 parasitizing thismetal member. However, the voltage of this counter electromotive forceis not applied to the second PN junction diode 12 a. The reason is thatthe anode of the second PN junction diode 12 a is connected to the anodeof the second Schottky barrier diode 22 by means of the connection metalwire 33. Only a voltage equivalent to the forward voltage Vf1 of thesecond Schottky barrier diode 22 is applied to the first PN junctiondiode 11 a. In other words, the second PN junction diode 12 a does notreceive a voltage greater than its forward voltage Vf2. Therefore, thecurrent does not flow through the second PN junction diode 12 a.

As described above, in the fifth embodiment, an electric current can berestrained from flowing through the PN junction diode 12 a built in thesecond MOSFET 12 when the first MOSFET 11 is changed from an ON state toan OFF state. Therefore, a forward direction deterioration of the MOSFET12 can be prevented.

The source of the first MOSFET 11 may be connected to the outputterminal 42 by means of the connection metal member 31, and the sourceof the second MOSFET 12 may be connected to the second power sourceterminal 43 by means of the connection metal member 33 in the same wayas in the first module 2B of the third embodiment. However, in thiscase, the inductances L1 and L3 parasitizing the connection metalmembers 31 and 33, respectively, are set to be greater than theinductances L2 and L4 parasitizing the connection metal members 32 and34, respectively.

The module 2 can also be used in a step-up DC-DC converter. In thiscase, a power source is connected to a portion between the terminals 42and 43 of the module 2, and a smoothing circuit consisting of a coil anda capacitor is connected to a portion between the terminals 41 and 43 ofthe module 2. Furthermore, a load is connected in parallel to thecapacitor. The gate terminal 44 of the first MOSFET 11 is groundedthrough a resistor. Thereafter, the second MOSFET 12 is switched. In thethus arranged stet-up DC-DC converter, when the second MOSFET 12 isturned off, an electric current does not flow through the PN junctiondiode 11 a of the first MOSFET 11 in the same way as in the step-downDC-DC converter mentioned above.

FIG. 8 is an electric circuit diagram showing a converter circuit 101Aaccording to a sixth embodiment of the present invention. In FIG. 8, thesame reference numeral as in FIG. 7 is given to a componentcorresponding to each component shown in FIG. 7.

The converter circuit 101A differs from the converter circuit 101 of thefifth embodiment in the arrangement of the module 2A. The arrangement ofthe module 2 of the fifth embodiment is the same as that of the firstmodule 2 of the first embodiment. On the other hand, the arrangement ofthe module 2A of the sixth embodiment is the same as that of the firstmodule 2A of the second embodiment.

Referring to FIG. 8, the source of the first MOSFET 11 (i.e., the anodeof the first PN junction diode 11 a) and the anode of the first Schottkybarrier diode 21 are connected to the output terminal 42 of the firstmodule 2A. The drain of the first MOSFET 11 (i.e., the cathode of thefirst PN junction diode 11 a) is connected to the cathode of the firstSchottky barrier diode 21 by means of the connection metal member 31Aparasitized by the inductance L1. The cathode of the first Schottkybarrier diode 21 is connected to the first power source terminal 41 ofthe module 2A by means of the connection metal member 32A parasitized bythe inductance L2. In other words, the cathode of the first Schottkybarrier diode 21 is connected to the first output line 17 through theconnection metal member 32A parasitized by the inductance L2.

The source of the second MOSFET 12 (i.e., the anode of the second PNjunction diode 12 a) and the anode of the second Schottky barrier diode22 are connected to the second power source terminal 43 of the module2A. The drain of the second MOSFET 12 (i.e., the cathode of the secondPN junction diode 12 a) is connected to the cathode of the secondSchottky barrier diode 22 by means of the connection metal member 33Aparasitized by the inductance L3. The cathode of the second Schottkybarrier diode 22 is connected to the output terminal 42 of the module 2Aby means of the connection metal member 34A parasitized by theinductance L4. In other words, the cathode of the second Schottkybarrier diode 22 is connected to the second output line 18 through theconnection metal member 34A parasitized by the inductance L4.

Each of the MOSFETs 11 and 12 is an SiC device in which, for example,SiC (silicon carbide) that is an example of a compound semiconductor isused as a semiconducting material. The forward voltage Vf1 of each ofthe Schottky barrier diodes 21 and 22 is lower than the forward voltageVf2 of each of the PN junction diodes 11 a and 12 a. The forward voltageVf2 of each of the PN junction diodes 11 a and 12 a is, for example, 2.0V. The forward voltage Vf1 of each of the Schottky barrier diodes 21 and22 is, for example, 1.0 V.

The gate terminal 45 of the module 2A is connected to the third outputline 19 through the resistor 71. A control unit (not shown) is connectedto the gate terminal 44 of the module 2A.

In the thus arranged converter circuit 101A, the first MOSFET 11 isturned on/off (is switched) at a predetermined duty ratio. When thefirst MOSFET 11 is turned on, an electric current flows from thepositive electrode of the power source 115 toward the load 116 throughthe first output line 17, the connection metal member 32A, theconnection metal member 31A, the first MOSFET 11, the second output line122, and the coil 72 (the smoothing circuit). As a result, energy isstored in the coil 72, and electric power is supplied to the load 116.

When the first MOSFET 11 is turned off, the coil 72 attempts to maintainan electric current flowing therethrough, and generates an electromotiveforce. This electromotive force allows the current to flow to the load116 through the second Schottky barrier diode 22 and the connectionmetal member 34A, and electric power is supplied to the load 116. Thisoperation is repeatedly performed, and, as a result, a voltage lowerthan the voltage of the power source 115 is applied to the load 116.

As described above, when the first MOSFET 11 is changed from an ON stateto an OFF state, an electric current flows through the connection metalmember 34A by an electromotive force generated by the coil 72. When thecurrent flows through the connection metal member 34A, a counterelectromotive force is generated by the inductance L4 parasitizing thismetal member. However, the voltage of this counter electromotive forceis not applied to the second PN junction diode 12 a. The reason is thatthe cathode of the second PN junction diode 12 a is connected to thecathode of the second Schottky barrier diode 22 by means of theconnection metal wire 33A. Only a voltage equivalent to the forwardvoltage Vf1 of the second Schottky barrier diode 22 is applied to thesecond PN junction diode 12 a. In other words, the second PN junctiondiode 12 a does not receive a voltage greater than its forward voltageVf2. Therefore, the current does not flow through the second PN junctiondiode 12 a.

As described above, also in the sixth embodiment, an electric currentcan be restrained from flowing through the PN junction diode 12 a builtin the second MOSFET 12 when the first MOSFET 11 is changed from an ONstate to an OFF state. Therefore, a forward direction deterioration ofthe MOSFET 12 can be prevented.

The drain of the first MOSFET 11 may be connected to the first powersource terminal 41 by means of the connection metal member 31A, and thedrain of the second MOSFET 12 may be connected to the output terminal 42by means of the connection metal member 33A in the same way as in thefirst module 2C of the fourth embodiment. However, in this case, theinductances L1 and L3 parasitizing the connection metal members 31A and33A, respectively, are set to be greater than the inductances L2 and L4parasitizing the connection metal members 32A and 34A, respectively.

Additionally, the module 2A can be used in a step-up DC-DC converter. Inthis case, a power source is connected to a portion between theterminals 42 and 43 of the module 2A, and a smoothing circuit consistingof a coil and a capacitor is connected to a portion between theterminals 41 and 43 of the module 2A. Furthermore, a load is connectedin parallel to the capacitor. The gate terminal 44 of the first MOSFET11 is grounded through a resistor. Thereafter, the second MOSFET 12 isswitched. In the thus arranged set-up DC-DC converter, when the secondMOSFET 12 is turned off, an electric current does not flow through thePN junction diode 11 a of the first MOSFET 11 in the same way as in thestep-down DC-DC converter mentioned above.

Although the six embodiments of the present invention have beendescribed above, the present invention can be embodied in other forms.For example, each of the MOSFETs 11, 12, 13, and 14 may be an Si devicein which Si (silicon) is used as a semiconducting material although eachthereof is an SiC device in the above embodiments.

Although the embodiments of the present invention have been described indetail as above, these are merely specific examples used to clarify thetechnical contents of the present invention, and the present inventionshould not be understood as being limited to these examples, and thescope of the present invention is to be determined solely by theappended claims.

The present application corresponds to Japanese Patent Application No.2010-121375 filed in the Japan Patent Office on May 27, 2010, and theentire disclosure of the application is incorporated herein byreference.

DESCRIPTION OF SIGNS

-   -   1, 1A, 1B, 1C Inverter circuit    -   2, 2A, 2B, 2C Module    -   3, 3A, 3B, 3C Module    -   11 to 14 MOSFET    -   11 a to 14 a PN junction diode    -   21 to 24 Schottky barrier diode    -   31 to 38, 31A to 38A, 31B to 38B, 31C to 38C Connection metal        member    -   72 Coil

The invention claimed is:
 1. A semiconductor device comprising: a firstchip including a PN junction diode; a second chip, including a Schottkybarrier diode, connected in parallel to the first chip; a firstconnection metal member having a first inductance, the first connectionmetal member having a first end to which a cathode of the PN junctiondiode is connected and a second end to which a cathode of the Schottkybarrier diode is connected; a second connection metal member having asecond inductance, the second connection member having a third end and afourth end, the third end being connected to the cathode of the Schottkybarrier diode; an output line connected to the fourth end of the secondconnection member, the output line being electrically connected to thecathode of the PN junction diode via a first electric path that isformed by the first and second connection metal members, and that has asum of the first and second inductances, the output line beingelectrically connected to the cathode of the Schottky barrier diode viaa second electric path that is formed by the second metal member andexclusive of the first metal member, and that has the second inductance;and a molding resin that seals the first chip and the second chiptherein.
 2. The semiconductor device according to claim 1, wherein thefirst chip is an SiC semiconductor chip made of a semiconductingmaterial that chiefly includes SiC.
 3. The semiconductor deviceaccording to claim 1, wherein a counter electromotive force generated bythe inductance between the second chip and the output line is 2.0 V ormore.
 4. The semiconductor device according to claim 1, furthercomprising a switching device connected to the PN junction diode ininverse parallel.
 5. The semiconductor device according to claim 4,wherein the first chip includes the switching device, the switchingdevice is a MOSFET, and the PN junction diode is built in the MOSFET. 6.The semiconductor device according to claim 1, wherein the connectionmetal member includes a wire.
 7. A semiconductor device comprising: afirst chip including a PN junction diode; a second chip, including aSchottky barrier diode, connected in parallel to the first chip; anoutput line connected to the first chip and to the second chip; amolding resin that seals the first chip and the second chip therein,wherein the first chip includes a MOSFET in which the PN junction diodeis built, an anode of the PN junction diode is connected to a source ofthe MOSFET, and a cathode of the PN junction diode is connected to adrain of the MOSFET; a first connection metal member having a firstinductance, the first connection metal member having a first end towhich the drain of the MOSFET is connected and a second end to which thecathode of the Schottky barrier diode is connected; and a secondconnection metal member having a second inductance, the secondconnection member having a third end connected to the cathode of theSchottky barrier diode and a fourth end connected to the output line,the output line being electrically connected to the cathode of the PNjunction diode via a first electric path that is formed by the first andsecond connection metal members, and that has a sum of the first andsecond inductances, the output line being electrically connected to thecathode of the Schottky barrier diode via a second electric path that isformed by the second metal member and exclusive of the first metalmember, and that has the second inductance.
 8. The semiconductor deviceaccording to claim 7, wherein a counter electromotive force generated bythe inductance between the second chip and the output line is 2.0 V ormore.
 9. The semiconductor device according to claim 7, wherein thefirst chip is an SiC semiconductor chip made of a semiconductor materialconsisting chiefly of SiC.
 10. The semiconductor device according toclaim 7, wherein the connection metal member includes a wire.
 11. Asemiconductor device comprising: a first chip including a PN junctiondiode; a second chip, including a Schottky barrier diode, connected inparallel to the first chip; a first connection metal member having afirst inductance, the first connection metal member having a first endto which an anode of the PN junction diode is connected and a second endto which an anode of the Schottky barrier diode is connected; a secondconnection metal member having a second inductance, the secondconnection member having a third end and a fourth end, the third endbeing connected to the anode of the Schottky barrier diode; an outputline connected to the fourth end of the second connection member, theoutput line being electrically connected to the anode of the PN junctiondiode via a first electric path that is formed by the first and secondconnection metal members, and that has a sum of the first and secondinductances, the output line being electrically connected to the anodeof the Schottky barrier diode via a second electric path that is formedby the second metal member and exclusive of the first metal member, andthat has the second inductance; and a molding resin that seals the firstchip and the second chip therein.
 12. The semiconductor device accordingto claim 11, wherein the first chip is an SiC semiconductor chip made ofa semiconducting material consisting chiefly of SiC.
 13. Thesemiconductor device according to claim 11, wherein a counterelectromotive force generated by the inductance between the second chipand the output line is 2.0 V or more.
 14. The semiconductor deviceaccording to claim 11, further comprising a switching device connectedto the PN junction diode in inverse parallel.
 15. The semiconductordevice according to claim 14, wherein the first chip includes theswitching device, the switching device is a MOSFET, and the PN junctiondiode is built in the MOSFET.
 16. The semiconductor device according toclaim 11, wherein the connection metal member includes a wire.
 17. Asemiconductor device comprising: a first chip including a PN junctiondiode; a second chip, including a Schottky barrier diode, connected inparallel to the first chip; an output line connected to the first chipand to the second chip; and a molding resin that seals the first chipand the second chip therein, wherein the first chip includes a MOSFET inwhich the PN junction diode is built, an anode of the PN junction diodeis connected to a source of the MOSFET, and a cathode of the PN junctiondiode is connected to a drain of the MOSFET; a first connection metalmember having a first inductance, the first connection metal memberhaving a first end to which the source of the MOSFET is connected and asecond end to which the anode of the Schottky barrier diode isconnected; and a second connection metal member having a secondinductance, the second connection member having a third end connected tothe anode of the Schottky barrier diode and a fourth end connected tothe output line, the output line being electrically connected to theanode of the PN junction diode via a first electric path that is formedby the first and second connection metal members, and that has a sum ofthe first and second inductances, the output line being electricallyconnected to the anode of the Schottky barrier diode via a secondelectric path that is formed by the second metal member and exclusive ofthe first metal member, and that has the second inductance.
 18. Thesemiconductor device according to claim 17, wherein a counterelectromotive force generated by the inductance between the second chipand the output line is 2.0 V or more.
 19. The semiconductor deviceaccording to claim 17, wherein the first chip is an SiC semiconductorchip made of a semiconductor material consisting chiefly of SiC.
 20. Thesemiconductor device according to claim 17, wherein the connection metalmember includes a wire.
 21. A semiconductor device comprising: a firstchip including a PN junction diode; a second chip, including a Schottkybarrier diode, connected in parallel to the first chip; an output line;a first connection metal member having a first inductance, the firstconnection metal member having a first end connected to a cathode of thePN junction diode and a second end connected to the output line; asecond connection metal member having a second inductance smaller thanthe first inductance, the second connection member having a third endconnected to a cathode of the Schottky barrier diode and a fourth endconnected to the output line; and a molding resin that seals the firstchip and the second chip therein.
 22. The semiconductor device accordingto claim 21, wherein the first chip is an SiC semiconductor chip made ofa semiconductor material consisting chiefly of SiC.
 23. Thesemiconductor device according to claim 21, wherein a counterelectromotive force generated by an inductance between the first chipand the output line is 2.0 V or more.
 24. The semiconductor deviceaccording to claim 21, further comprising a switching device connectedto the PN junction diode in inverse parallel.
 25. The semiconductordevice according to claim 24, wherein the first chip includes theswitching device, the switching device is a MOSFET, and the PN junctiondiode is built in the MOSFET.
 26. The semiconductor device according toclaim 21, wherein the connection metal member includes a wire.
 27. Asemiconductor device comprising: a first chip including a PN junctiondiode; a second chip, including a Schottky barrier diode, connected inparallel to the first chip; an output line; a first connection metalmember having a first inductance, the first connection metal memberhaving a first end connected to an anode of the PN junction diode and asecond end connected to the output line; a second connection metalmember having a second inductance smaller than the first inductance, thesecond connection member having a third end connected to an anode of theSchottky barrier diode and a fourth end connected to the output line;and a molding resin that seals the first chip and the second chiptherein.
 28. The semiconductor device t according to claim 27, whereinthe first chip is an SiC semiconductor chip made of a semiconductormaterial consisting chiefly of SiC.
 29. The semiconductor deviceaccording to claim 27, wherein a counter electromotive force generatedby an inductance between the second chip and the output line is 2.0 V ormore.
 30. The semiconductor device according to claim 27, furthercomprising a switching device connected to the PN junction diode ininverse parallel.
 31. The semiconductor device according to claim 30,wherein the first chip includes the switching device which is a MOSFET,and the PN junction diode is built in the MOSFET.
 32. The semiconductordevice according to claim 30, wherein the connection metal memberincludes a wire.